Protractor



(No Model.)

P. KENNELLY.

PROTRAGTOR. No. 285,907. Patented Oct. 2, 1883.

e'nds which are UNITED STATES PATENT Crrrcie.

PATRICK KENNELLY, OF BRIDGEPORT, CONNECTICUT.

PROTRAC'TOR'.

sencrrrcn'rron forming part of Letters Patent No. 285,907, dated October2,1883.

Application filed February 20, 1583. (No model.)

To all whom it nmyconcern:

Be it known that I, PATRICK KENNELLY, a citizen of the United States,residing at Bridge port, in the county of Fairfield, State ofConnecticut, have invented an Improved Protraetor, of which thefollowing is a specification.

My invention relates to that kind of a protractor in which there is arevolving center and a straight edge, whereby machinists and otherartisans may use their plain bevel-square in determining the differentangles.

' The object of my invention is to provide a tool for accuratelydetermining all angles, in connection with the common bevel-square,which is a part of the usual outfit of all ironworkers.

In the drawings forming a part of this specification, Figure l is a planview of the protractor graduated from ninety degrees at right angles tothe base-line a b to 0 at each of the parallel to the baseline,substantially as shown. Fig. 2 is an edge view of Fig. 1. Fig. 3 is anenlarged view ofswive1- center. ,Fig. at is an enlarged cross-section ofFig. 3, showing the upper portion out to the center at a. Figs. 5 and 6are a plan and elevation of screw for fastening Fig. 3 to Fig. 1, asshown in Fig. 2 at b.

To operate the device it is only necessary to place one edge of thebevel-square on the edge a b, Fig. 1, then bring the blade against theface of that part of Fig. 3 which is shown in cross-section at a, Fig.4.. found that the blade will stop in the center and register the angleaccurately on either side of the perpendicular.

I am aware that prior to my invention protractors have been used bydraftsinen and others; those, however, cannot be used by inachinists,tool-makers, and a large class of other tradesmen, each of whom have aplain bevelsquare, which, with the use of my invention, will enable themto use it to advantage; but I am not aware that any with a revolvingse1f-adjusting center has been used therefore I claim- 1. Thecombination of the revolving center, Fig. 3, the upper part of which iscut away to the center, as shown, and the graduated are, as and for thepurpose described.

' 2. The combination of the graduated arc, Fig. 1, and self-adjustingcenter, Fig. 3, one half of which is removed to the center, as shown ata, Fig. 4, with edge of Fig. 1, so that the center will adjust itself toany angle de sired, substantially as shown.

PATRICK KENNELLY.

It will then be

